The present invention relates to a semiconductor device, and to the method for manufacturing the same.
FIG. 9 shows a schematic diagram of a conventional semiconductor device molded with resin. FIG. 10 shows a top-view of the semiconductor device. These drawings show a Quad Flat Package (QFP).
This semiconductor device has a first semiconductor chip 91, a second semiconductor chip 92, a die pad 93, a first adhesive layer 94, a second adhesive layer 95, electrodes 96 on the first semiconductor chip, electrodes 97 on the second semiconductor chip, inner leads 98, metal wires 99,910, a package portion 912, outer leads 913, and a pad support portion 914. The semiconductor chips 91 and 92 are stacked on a die pad 93.
The die pad 93 is lower than the inner leads 98 as shown in FIG. 9 and FIG. 10. The hanging portion of the pad support portion 914 is bent, and the die pad and the inner leads are not at the same level. The bent portion is indicated by reference numeral 1011 in FIG. 10, this structure is called a downset. The thickness t1 of the resin on the semiconductor chip 92 is the same as the thickness t2 of the resin under the die pad 93 in the conventional design. The resin is filled proportionally during transfer molding because the thickness of resin on the semiconductor chip 92 and the thickness of resin under the die pad 93 are the same. Therefore, a short-circuit of wires on the semiconductor chip 91 and the semiconductor chip 92 is prevented. The warping of the package is also prevented.
The semiconductor chip 91 is fixed over the die pad 93 by the first adhesive layer 94. The semiconductor chip 92 is fixed over the semiconductor chip 91 by the second adhesive layer 95.
The electrodes 96,97 on each of the semiconductor chips are connected to inner leads 98 via metal wires 99,910. For example, gold wires connect electrodes and inner leads. Some electrodes 97 on the semiconductor chip 92 are connected to the electrodes 96 on the semiconductor chip 91. After the wire bonding, a resin (for example, epoxy resin) is molded on semiconductor chips. After the forming of the package portion 12, the outer leads are plated with solder. The outer leads 913 are then transformed into a predetermined form.
An object of the present invention is to provide a semiconductor device and the method for manufacturing the same that do not need a downset process. Therefore the yield is improved during the formation of a lead frame.
According to an embodiment of this invention, a semiconductor device comprises, a die pad having a top surface and a bottom surface, a first semiconductor chip having a top surface on which electrodes are formed and a bottom surface, and a second semiconductor chip having a top surface on which electrodes are formed and a bottom surface, the second semiconductor chip being smaller than the first semiconductor chip, wherein the top surface of the first semiconductor chip is fixed on the bottom surface of the die pad, the bottom surface of the second semiconductor chip is fixed on the top surface of the die pad.
A method for manufacturing the semiconductor device comprises forming a first adhesive layer on a bottom surface of a die pad, forming a second adhesive layer on a top surface of the die pad, fixing a top surface of a first semiconductor chip on the first adhesive layer, fixing a bottom surface of a second semiconductor chip which is smaller than the first semiconductor chip on the second adhesive layer.